Art of cracking hydrocarbon oils



May 26, 1931. E. w. lsoM ART OF CRAGKING HYDROCARBON OILS Original FiledSept. 27, 1927 3 Sheets-Sheet 1 MN NN,

INV Ed/f/ardI/Kfalm BY /Wnlla/ 9M@ MVM ATTORNEYS 'May 26,v 1931. E. w.lsoM ART OF CRCKING HYDROCAHBON OILS Original Filed Sept. 27, 1927 3Sheets-Shadi. 2

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INVENTOR fda/ard Misa/77 ATTORNEYS May 26, 1931. E. w. lsoM ART OFCRACKING HYDROCARBON OILS 3 Sheets-Sheet 3 Original Filed Sept. 27, 1927MN NN INV ATTORNEYS Pwwk h Patented May 26, 1931 Unirse stares rarestorties EDWARD W. ISOM, OF SCARSDALE, NEW' YORK, ASSIGNB TO SNCLAIRREFINING- COM- PANY, OF NEW YORK, N. Y., A CURPGRATIGN OF MANE ART 0FCRACKING HYDROGARBON OILS Original application led September 9.7, 1927,Serial No. 222,257. Divided and this application filed Beeemlcer 7,1929.

rlhis invention relates to improvements in the cracking of heavier andhigher boiling hydrocarbon oils, such as gas oil, for the productiontherefrom of lighter and lower boiling hydrocarbon oils, such asgasoline. This application is a division of application Serial Number222,25", filed September 27th, 1927.

More particularly, this invention relates to improvements in thecracking of heavier and higher boiling hydrocarbon oils by distillationunder pressure as described in Letters Patent Number 1,634,666, issuedto the Sinclair Refining Company, July 5th, 1927, on an application ofEugene C. l-lerthel and Harry L. Pelzer.

According to the present invention, a charge of oil is circulated andrecirculated from a bulk supply drum through heating tubes and back tothe bulk supply drum and a bed of absorbent or filtering ordesulphurizing material is maintained inthe bulk supply drum extendingentirely across the path of the circulating'charge of oil, the oil isheated to a cracking temperature in the heating tubes and vapors aretaken off from the bulk supply drum under pressure, and circulation ofthe charge of oil is promoted by maintaining a substantial pressure dropthrough the bed of absorbent or filtering or desulphurizing material.

This maintenance of a substantial pressure di'erential through the bedof absorbent or filtering or desulphurizing material is one'of theimportant Jfeatures of the present invention and, in the combinedoperation, contributes to several important advantages pertaining to theinvention.

One particularly advantageous way of maintaining this. pressuredifferential is to take off vapors from the bulk supply drum above thebed of absorbent or filtering or desulphurizing material under pressureand to take ofi1 vapors from beneath the bed under a lower pressure. Thevapors from above the bed and from below the bed may then be separatelydischarged and refluxed in separate reflux towers, from which refluxcondensates are returned to the circulating charge of oil.

he invention thus provides improvements which relate particularlyto-circulation of Serial No. 416,795.

the charge of oil undergoing pressure distillation. rhe invention,however, also includes several other improvements which will be apparentas the description proceeds.

The invention will be further and more particularly described bydescription of several diiierent operations embodying various featuresof the invention. It is intended and will be understood that this moredetailed description is by way of example and that the invention is notspecifically limited to the particular operations described or tooperations carried out in the particular apparatus described.

IThe accompanying drawings illustrate, diagrammatically andconventionally, several forms of apparatus adapted for carrying outdifferent operations embodying the invention, and different features ofthe invention, and the invention will be further described in connectiontherewith. Each of the three figures oit drawings represents, inelevation and partly in section and with parts broken away, a pressurestill system adapted for carryinoout an operation embodying theinvention.

The pressure stillproper, in the apparatus illustrated in the drawings,is of the general type described in Letters Patent Number 1,634,666,mentioned above. This pressure still comprises a bulk supply drum 1, abattery of heating tubes 2, and circulating connections 3, 4c and 5including circulating pump 6 for circulating oil from the bulk supplydrum upwardly through the heatingv tubes and back to the bulk supplydrum, The heating tubes 2 are arranged in the heating flue of a furnace7. A support 8 adapted to permit tree passage of oil but to retainfinely divided solid material is arranged in the bulk supply drum andextending entirely across the bulk supply drum between the circulatingconnectionsB to the battery of heating tubes and the circulatingconnections 5 from the battery of heating tubes. In operation, a bed offinely divided absorbent or filtering or desulphurizing material isarranged on this support so as to be submerged inthe body of. oil in thebulk supply drum. The bulk supply drum 1 and-the circulating connectionsroo ' mally insulated to minimize heat loss.

1927, by Thomas de Colon Tiift, are particu-Y initially charging thestill and Another advantageous form of support for the bed of finelydivided solid material is described in application Serial Number184,296, filed April 16th, 1927, by Harry L. Pelzer.

The pumps described in applications Serial Numbers 197,209 and 197,210,filed J une 7th,

lai-ly adapted for use as circulating pumps in carrying out the presentinvention.

A battery of heating tubes of the type de scribed in application SerialNumber 197,035, liled J une 7th, 1927, by Harry L. Pelzer, may besubstitutedfor the battery of heating tubes illustrated.

Connection is provided for discharging pitch laden oil or tar during theoperation, as described in Letters Patent Number 1,634,666, mentionedabove. This connection may be arranged to discharge tar from above thebed of finely divided solid material or from below the bed of finelydivided solid material (see Figs. 2 and 3) Connection 10 is provided forfor pumping out the still at the end of a run.

Connections 11, with suitable forcing means, are provided forrecirculating over the heating tubes in admixture with fresh hotproducts of combustion from the lire-box of the furnace a part of theheating gases which have passed thereover as described in Letters PatentNumbers 1,574,546 and 1,574,547, issued to the Sinclair RefiningCompany, Febguary 23rd, 1926, on applications of John ell.

The bed of finely divided material carried on the support'S maycomprise, for example, 15-30 mesh fullers earth in a depth of from 7 to18 inches. In place of fullers earth, other absorbent clays may be used.Other absorbent or filtering or desulphurizing materials useful incarrying out the invention include ground' coke, iron oxide, calcinedbauxite and silica gel.

The features of the pressure still proper just, described are common tothe several pressure still systems illustrated in the several figuresand corresponding parts have been designated by the same referencecharacters in the several figures.

Referring more particularly to Fig. 1, two reflux towers, 30 andY 31,are arranged above the bulk supply drum 1. These towers may be ofordinary baliie construction, as illustrated. Vapors from the upper partof the bulk supply drum 1 escape into the lowerend of the tower 30through connection 13, this connection including a pressure reducing andregulating valve 14. Vapors from beneath the support 3 and thesuperimposed bed of finely divided material escape through the vaporpassage 15 and connection 16into the lower end of the tower 31. Thereflux towers 30 and 31 areadvantageously lagged or thermally insulated.Connections 32 and 33 are provided for the direct introduction of arefluxing medium into the upper ends of the towers 30 and 31respectively. By means of the pump 34, the reflux condensate or oilmixture from tower 30 may be introduced into the charge of oil in thestill either through connection 35 or through connection 36 or partlythrough both of these connections. Similarly, by means of the pump 37,the reflux condensate or oil mixture from tower 31 may be introducedpartly or wholly either through connection 35 or through connection 36or through connection 38 into'the reflux tower 30 at an intermediatepoint. The refluxing in either or both of the towers 32 and 33 may alsobe effected or controlled by indirect heat exchange with a suitablerefluxing medium. Raw oil,for example, may be supplied to the o-perationby introduction through either or both of the towers 30 and 31, or rawoil may be supplied through the bearings of the circulating pump 6 bymeans of connection 19, or raw oil in additionA to that introducedthrough the towers 30 and 31 may be supplied through connection 19.Vapors from the reflux tower 30 escape through connection 39 tocondenser 21 which in turn discharges into receiver 22.V Fromthis/receiver the distillate product is discharged through connection 23and any uncondensed vapors and gases through connection 24. Vapors'fromthe reiux tower 31 escape through connection 40 to a condenser andreceiver (not shown) of construction and arrangement similar to that ofcondenser 21 and receiver 22. The pressure may be reduced between thereiiux tower 30 and the condenser 21 by means of 'valve 25, or thepressure prevailing in thisreliux tower may be and reduced by means ofsuitable valves arranged beyond the condenser or receiver; the pressuremay be reduced between the refluxV tower 31 and the condenser with whichit communicates through connection 40 by means of valve 41, or thepressure prevailing in this reflux tower maybe maintained through 'theconnected condenser and reduced by means of similar valves arrangedbeyond the condenser or receiver.

In one way of carrying out the invention in apparatus ofthe typeillustratedI in Fig. 1, for example, the still is initially charged withsay about 8,000 gallons of gas oil and brought to cracking conditions oftemperature and pressure in the usual way. ln such operation, the

bed of finely ldivided solid material may con` sist of from 4 to 7tonsof 15-30 mesh fullers earth. v After the still is brought tocracking conditions of temperature and pressure, vapors are permitted toescape from the upper part of the bulk supply bed into tower 30 throughconnection 13 and vapors from beneath the bed of absorbent Yor filteringor desulphurizing material `are permitted to maintained through thecondenser L ing stocks.

escape into tower 31 through connection 16 and the introduction of rawoil through connections 32 and 33 is begun. Vhen the introduction of rawoil is begun, or shortly thereafter, the discharge of pitch laden oil ortar through connection 9 is also started. At this point in the operationdistillate may be taken olf at a rate of about 1,000 gallons per hour orsomewhat more, tar discharged at a rate of about 1,500 gallons per houror somewhat less, and raw oil supplied at a rate. or" about 2,500gallons per hour. From 100 to 500 gallons per hour or somewhat more ofthis raw oil may be supplied through connection 19 and the balancethrough connections 32 and 33. The pressure under which the vapors aretaken ofln from the upper part of the bulli supply drum is maintained ata higher value than pressure under which the vapors are taken ofi" frombeneath the bed. The pressure in the upper part of the bulk supply drumVis advantageously maintained in the neighborhood of from 250 to 300pounds per square inch, for example, while the space in the lower partof the bulk supply drum, beneath support S, is maintained at a pressureapproximately 10 to 20 pounds per square inch less. This pressure may bemaintained by regulation of the discharge of vapors through connections13 and 16 by valves 14 and 42 respectively, or by maintainingappropriate pressures in the two reflux towers by valves located beyondthe reflux towers, for example valves 25 and 41, while maintainingsubstantially free communication between the upper part of the bulksupply drum and the reflux tower 30 through connection 13, and betweenthe lower part of the buik supply drum and the reux tower 31 throughconnection 16. The resulting pressure differential between the upperpart of the bulk supply drum and the lower part of the supply drum actsto drive the unvaporized oil discharged from the battery of heatingtubes under pressure from the circulating pump 6 through the bed ofabsorbent or filtering or desulphurizing material into the lower` partof the bullr supply drum to be recirculated through the battery ofheating tubes. Due to the drop in pressure through the bed of earth orfinely divided solid material, additional vaporization takes place inthe lower part of the bulk supply l drum and these vapors escape throughvapor passage 15 and connection 16.

It is intended and will be understood that the operation just described,particularly the figures as to amounts and pressures, is given simply byway of illustration. The several features of the invention embodied inthis operation may also be embodied in other operations carried out inother apparatus, at diierent pressures and with different charg- Bymaintaining the pressure in the bulk supply drum beneaththe bedofabsorbent or ltering or desulphurizing material at a lower value thanthat prevailing in the upper part of the bulk supply drum, circulationof the still charge is promoted. Among the resulting improvements inopera-tion may be mentioned higher velocity through the heating tubeswith consequent improvement in uniformity of rate of heat transfertherethrough as well as an increase in the effective contact between thecirculating still charge and the bed of absorbent or filtering ordesulphurizing material. he drop in pressure through the bed ofabsorbent or ltering or desulphurizing material also assists invaporizing from the oil about to be recirculated through the heatingtubes lighter constituents, particularly constituents suitable ascomponents of the desired distillate product, which might otherwise besubjected to overcraclring with consequent loss if recirculated throughthe heating tubes. rl`he constituents vaporized from beneath the bed,however, also assist in promoting circulation through the bed ofabsorbent, filtering or desulphurizing material.

During operation, pitch laden oil or tar may be discharged from the bodyof oil in the bulk supply drum, either from above or from below the bedof absorbent or filtering or i desulphurizing material submerged thereinand extending thereacross. Pitch laden oil or tar discharged from abovethe bed of absorbent or filtering ordesulphuriZing ma-v terial containsa greater concentration of constituents absorbable or removable by theaction of the bed than pitch laden oil or tar discharged from below thebed. However, in some cases, circulation of the still charge may befurther promoted by discharging pitch laden oil or tar from beneath thebed of absorbent orl filtering or desulphurizing material, the oilcomponents of the discharged tar in such operation assisting in dilutingthe suspension or solution of pitch or pitchy or carbonaceous materialcirculating thro-ugh the bed. l

The reux condensate or oil mixture from tower 30 is advantageouslyreintroduced into the circulating charge of' oil through connection 36;where this stock is relatively refractory it is thus again heated to thecracking temperature before it can again escape from the pressure stillproper as vapors. Or this reflux condensate or oil mixture, or part ofit, may be reintroduced into the circulating charge of oil throughconnection 35 to assist in promoting circulation as previouslydescribed. For example, the reflux condensate or oil mixture from tower30 initially may be reintroduced into the circulating charge of oilentirely or largely through connection 36 and at a later period in theloperation may be introduced, or introduced in increased proportion,throughv connection 35. The reflux condensate from tower 31 is usuallyless refractory than that from tower 30, and also is usually somewhatheavier and higher boiling than the reflux condensate from tower 30.This reflux condensate, or the oil mixture containing this reduxcondensate, from tower 3l, or part of it, may be reintroduced int-oreflux tower through connection 38 'there to assist in the reuxingoperation carried out in tower 30 and at the same time to be stripped ofany light constituents suitable as components of the desired product. Inthis operation, the reflux condensate or oil mixture from tower 31 sointroduced into tower 30 is supplied to the circulating charge of oil inadmixture with the reflux condensate produced in tower 30; thiscomposite mixture, for example, may be reintroduced into the circulatingcharge of oil either through connection 35 or through connection 36 orthrough both of these connections, as previously described. The refluxcondensate or oil mixture from tower 3l, or part of it, may also bereintroduced into the circulating charge of oil 'directly throughconnection 36. This reflux condensate or oil mixture from tower 3l, orpart of it, may also be reintroducedinto the charge of oil in the bulksupply drum above the bed of absorbent or filtering or desulphurizingmaterial through connection 35. lVhen this reflux condensate or oilmixture is relatively less refractory, it may thus be reheated to a temerature sufficientl to produce useful crac ring by the hot oil productsdischarged from the battery of heating tubes at the same time assistingin promoting circulation Vof the still charge. rlhe two refluxingoperations may each be effected and controlled by the regulate-dintroduction of raw oil or, if the total amount of raw oil to besupplied to the operation is insufficient, by the regulated introductionof raw oil in admixture with a part of the distillate product or afraction of corresponding character. One advantageous mode ofoperationis to introduce as much raw` oil as possible, within the limitsofthe requiredrefluxing, into tower 3l, to effect and regulate therefluxing in tower 30 by the introduction of the balance of the raw oilor part of it or such ra-w oil in admixture with a part of thedistillate product or a fraction of correspon-ding character, and tointroduce any remaining raw oil through connection 19.

In general it is advantageous to operate the two towers and to handlethe reflux condensate or oil mixture from each of the two towers so thatstocks of corresponding character are kept togetherand are subjected tothose conditions prevailing in the system most appropriate for thetreatment of the particular stock.V For example, where the refluxing intower 30'iselfected largely or en tirely by the introduction of a partof the dis` L tillate product or a fraction of correspondingY character,the reflux condensate from this` tower is usually relatively refractoryand is advantageously returned largely or entirely through connection36. Where a substantial proportionof raw oil of relatively lessrefractory character is introduced into reux tower 30, the resulting oilmixture containing the reflux condensate, or a larger portion of it,'maywith advantage be reintroduced through connection 35. Usually, however,it is advantageous to supply stock reintroduced through connection 35largely or entirely from reflux tower 3l, as this stock tends to berelatively less refractory, the more refractory stock from tower 30being reintroduced through connection 36. Similarly, it is frequentlyadvantageous to effect the refluxing in tower 30 entirely by theintroduction of a part. of the distillate product or a fraction ofcorresponding character and to introduce the raw oil to be supplied tothe operation, or as much of it as may be so introduced within thelimits of the desired refluxing, into the tower 3l where the relativelyless refractory components of the raw oil mix with the relatively lessrefractory refiux condensate from the vapors escaping from beneath thebed of absorbent or filtering or desulphurizing material. The relativelyless refractory stocks may thus be concentrated in thc oil mixture'produced in tower 3l and the relatively more refractory stocksconcentrated in the oil mixture produced in tower 30.

rlhe apparatus illustrated in Fig. 2 is similar to the apparatusillustrated in Fig. l except in the provision of an auxiliary bank ofheating tubes arranged in the heating furnace between the Jirebox andthe heating flue in which the battery of heating tubes 2 are located,asV described in application Serial Number 664,502, filed September24th, 1923, by Eugene GrHerthel. and in the provision of means forhandling the vapors separated from the pitch laden oil or tar discharged.from the cracking operation during distillation.

tail in the further description of the appa` The latter feature isdescribed in deratus illustrated in F ig. 3. The auxiliary bank ofheating tubes 43 is arranged in the path of the heating gases in thefurnace so that the heating gases while at highest temperature andbefore they pass over the battery "of heating tubes` 2 pass over theseauxiliary ioo iio

to advantageous cracking conditions, particularly where the stock isrelatively refractory. In the apparatus illustrated in F ig. 2,connections including a suitable forcing means are provided forcirculating the reliux condensate or oil mixture from reflux tower 30through the auxiliary bank of heating tubes 43 and thence into the bulksupply drum of the pressure still proper. The reflux condensate or oilmixture discharged from the tower through connection is forced by meansof the pump 45 through connection 46 to and through the auxiliaryheating tubes 43 and thence through connection 47 and circulatingconnections into the upper part of the bulk supply drum l.

In one way of carrying out the invention in apparatus of the typeillustrated in Fig. 2, after the still is brought to cracking conditionsof temperature and pressure in the usual way, vapors are permitted toescape through connections 13 and 16 into reflux towers 30 and 31respectively and a pressure differential is maintained through the bedof absorbent or filtering or desulphurizing material in the bulk supplydrum as has been described in connection with the operation of theapparatus illustrated in F ig. 1. Raw oil, particularly relatively lessrefractory raw oil, is introduced into tower 31 through connection 33and the resulting oil mixture containing the rei'iux condensate producedin this tower is supplied to the circulating charge of oil in thepressure still proper either through connection 36 or through connection35 or partly through both of these connections as has been described.rlhe reflux condensate from tower 30 is forced through the auxiliaryheating tubes 43 and thence into the bulk supply drum by means of pump45. If at any time the supply of reflux condensate is insuflicient, itis supplemented by raw oil supplied through connection 48, or raw oil ofa relatively more refractory character may be supplied regulan lythrough this connection during the operation to be passed through theauxiliary heating tubes 43 in admixture with the reflux condensate fromtower 30. Raw oil may also be supplied to the heating tubes 43 throughconnection 48 while the still is being brought to operating conditions.The refluxing operation in tower 30 is advantageously carried out byintroducing into the tower a part of the distillate product or afraction of corresponding character, or relatively more refractory rawoil may be introduced into tower 30, alone or in admixture with suchother refluxing medium, to eect or control the operation. Where severalstocks are to be treated, the relatively less refractory stocks may thusbe supplied to tower 31 through connection 33 and the relatively morerefractory stocks to tower 30 through connection 32, the resultingrelatively more refractorv oil mixture produced in tower 30 thus beingsubjected to the more severe cracking conditions prevailing in theauxiliary bank of heating tubes. Y

The pitch laden oil or tar discharged during the operation may bereduced to coke in an externally fired shell still at atmosphericpressure and the distillate so produced returned to the operation, forexample, or this pitch laden oil or tar may be distilled largely orentirely by its self-contained heat as it is discharged during theoperation by reduction in pressure thereon while still at hightemperature, for example, as described in application Serial Number117,697, led d une 22nd, 1926, by Eugene C. Herthel and Thomas de ColonTiift. VVhere the pitch laden oil or tar discharged from the operationis subjected to distillation and the distillate is returned to thecracking operation, it is advantageous to strip the distillate of anylight constituents such as are suitable as components of the desiredproduct or which are too refra-ctory for useful treatment in theoperation. In the operation of pressure still systems of the typeillustrated in Figs. 1 and 2, the vapors formed during the distillationof the discharged pitch laden oil or tar may with advantage beintroduced together with the vapors escaping from beneath the bed ofabsorbent or filtering or desulphurizing material into the reflux towerto which the latter vapors are conveyed. The heavier vaporizedcomponents of the discharged pitch rladen oil or tar are usuallyrelatively less refractory and may thus be handled with advantage inadmixture with the reflux condensate from t-he heavier vapors dischargedfrom beneath the bed of absorbent or filtering or desulphurizingmaterial.

The apparatus illustrated in Fig. 3 provides for handling the vaporsseparated from the pitch laden oil or tar discharged from the crackingoperation during distillation of the same in the refluxtower into whichthe vapors from beneath the bed of absorbent or filtering ordesulphurizing material escape. The pitch laden oil or tar dischargedeither from above the bed through connection 9a or from beneath the bedthrough connection 9b is discharged into a vaporizing receptacle 49through a pressure reducing valve, the pressure in the vaporizingreceptacle being maintained at a value low enough to effect thevaporization of the components to be returned to the cracking operationbut advantageously high enough so that residue remaining can bedischarged as a liquid. The residue remaining unvaporized in thevaporizing receptacle 49 is discharged through connection 50. The vaporsseparated in this receptacle escape through connection 51 into the lowerend of tower 31. The vapors escaping from beneath the bed of absorbentor filtering or desulphurizing material also enter the lowerend of thistower through connection 16. The pressure in the reflux tower 3l, andlconsequently the pressure in the vaporizing rceeptacle 49, is regulatedby means of valve 4l or by other suitable valves arranged beyond thereux tower. Usually it -is advantageous to' subject the discharged pitchladen oil or tar to a much greater 1pressure drop than is maintainedthrough the bed of absorbent or filtering or desulphurizing materia-l,and for this reason it is usually necessary to reduce the pressure onthe vapors vescaping through the vapor passage l5 from beneath the bedby means of valve l2 before these vapors enter the reflux tower 3l. Thepressure in the vaporizing receptacle 191, for example, may bemaintained in the neighborhood of atmosphericl pressure or at a somewhathigher value. Otherwise, the operation may be conducted in substantiallythe same manner as has been described in connection with the operationof the apparatus illustrated in Fig. l. The vaporizing receptacle i9 isadvantageously lagged or thermally insulated to maintain the temperaturetherein.

I claim:

l. An improved method of cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of finely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, taking ofi vapors from the upper part of the bulksupply drum under pressure and subjecting these vapors to a refluxingoperation, and taking off vapors from beneath said bed under a lowerpressure and subjecting these vapors to a separate refluxing operation.

2. An improved method of cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of linely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, takingoff' vapors from the upper part of the bulksupply drum under pressure and subjecting these vapors to a reiuxingoperation and returning reflux condensate therefrom to the circulatingoil, and taking o vapors from beneath said bed under a lower pressureand subjecting these vapors to a separate refluxing operation andreturning reflux condensate therefrom to the circulating oil beneathsaid bed.

3. An improved method of cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of finely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, taking off vapors from the upper part of the bulksupply drum under pressure and subjecting these vapors toy a refluxingoperation and returning reflux condensate therefrom to the circulatingoil, and taking off vapors from beneath said bed under a lower pressureand subjecting' these vapors to a separate reuxing operation andreturning reflux condensate therefrom to the upper part `of the bulksupply drum.

4. An improved method of cracking hydrocarbon oils, Awhich'comprisescirculating the oil from a bulk supply 'drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of finely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil. taking off vapors from the upper part ofthe bulk supplydrum under pressure and subjecting these vapors to a refluxing operation'and returning reflux condensate therefrom to the circulating oil, andtaking off vapors from beneath said bed under a lower pressure andvsubjecting these vapors to a. separate `refiuxingoperation andintroducing reflux condensateth'erefrom into the vapors in the firstmentioned refluxing operation.

5. An improved method of cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a. body of nely divided solid materialin the bulk supply drum extending entirely across the path'of thecirculating' oil. taking off vapors I from the upper part of the bulksupply drum under pressure and subj ecting'these vapors to refiuxingoperation, taking olf vapors from beneath said bed under a lowerpressure and subjecting ythese vapors to a separate refiuxing operation,and introducing raw oil into the vapors in the second mentionedrefluxing operation. i

6. An improved method of cracking hydrocarbon oils, which comprisescirculatingfthe oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining abed of finely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, taking off vapors from the upper part of the bulksupply drum under pressure, taking off vapors from beneath said bedunder a lower pressure, subjecting the vaporsso taken off to a refluxingoperation, and reintroducing reflux therefrom into the circulating oilduring an earlier period of the operation beneath said bed and during alater period of the operation above said bed.

7. An improved method ot cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through eating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of finely divided solid materialin the bull: suppiy drum extending entirely across the path of thecirculating oil, taking ottn vapors from the upper part of the bulksupply drum under pressure and subjecting these vapors to a refluXingoperation, taking oit vapors from beneath said bed under a lowerpressure and subjecting these vapors to a separate reiiuX- ingoperation, returning reflux condensate from the first mentionedretluXinff operation to the bulk supply drum through separate heatingtubes, and passing heating gases for supplying heat to the operationfirst over these separate heating tubes and then over the firstmentioned heating tubes.

8. An improved method ot cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a crackin@` temperaturein the heating tubes, maintaining a bed ot finely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, taking ott vapors from the upper part of the bull;supply drum under pressure and subjecting these vapors to a refluxingoperation, introducing raw oil into the vapors in this refluxingoperation, taking ofi vapors :from beneath said bed under a lowerpressure and subjecting these vapors to separate retluxing operation,returning admired reiiuX condensate and raw oil from the first mentionedrefiuxing operation to the bulli supply drum through separate heatingtubes, and passing heating gases tor supplying heat to the operationiirst over these separate heating tubes and then over the firstmentioned heating tubes.

9. An improved method ot cracking hydro carbon oils, which comprisescirculating the oil from a bull; supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperaturein the heating tubes, maintaining a bed of nely divided solid materialin the bulk supply drum extending entirely across the path of thecirculating oil, taking o vapors from the upper part of the bulk supplydrum under pressure and subjecting these vapors to a retluxingoperation, taking o vapors from beneath said bed under a lower pressureand subjecting these vapors to a separate retluxing operation,introducing :ra-W oil into the vapors in this separate refluxingoperation, returning reflux condensate from the first mentionedrefluXing operation to the bulk suppiy drum through separate heatingtubes and passing heating gases tor supplying heat to the operationfirst over these separate heating tubes and then over the firstmentioned heating tubes. i

l0. An improved method ot cracking hydrocarbon oils, which comprisescirculating the oil from a bulk supply drum through heating tubes andback to the bulk supply drum, heating the oil to a cracking temperauture in the heating tubes, maintaining a bed ot iinely divided solidmaterial in the bulk supply drum extending entirely across the path ofthe circulating oil, taking ofi" vapors from the upper part of the bull;supply drum under pressure and subjecting these vapors to a retluxingoperation, taking off vapors from beneath said bed under a lowerpressure and subjecting these vapors to a separate refluxing operation,returning reflux condensate from the first mentioned refluxing operationto the bulk supply drum', discharging pitchv laden oil from thecirculating oil during operation and reducing the pressure on thisdischarged pitch laden oil While still at high temperature, andintroducing the vapors so separated from the discharged pitch laden oilinto the second mentioned refluxing operation.

ln testimony whereof l affix my signature.

EDWARD W. lISOM.

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